Modeled estimates of altered hydrologic metrics for all NHDPlus v21 reaches in the Chesapeake Bay watershed

Data are modeled estimates of flow status (inclined, diminished, or indeterminant) for 12 published hydrologic metrics (HMs) that characterize main components of flow regimes (duration, frequency, magnitude, timing, and rate of change). Model estimates came from random forest models independently built for each HM that predict flow status category using drainage area and previously summarized upstream catchment accumulated values (NHDPlus v2.1, 1:100,000 scale) for 15 landscape variables that describe anthropogenic stress related to urban development, agriculture, water usage and augmentation, and drainage area. HM observed data came from Eng et al. (2019) who published quantitative and categorical estimates of hydrologic alteration for each of twelve HMs for 3,355 USGS gages across the contiguous U.S.A. Estimates included in this data release were based on a subset of 1,235 gages that were located in four aggregated Level III ecoregions within the Chesapeake Bay watershed. See Maloney et al. (XXXX) for a more detailed description of model approach, background data, results and application to a biological endpoint.